The answer to fundamental questions about the organization of the language comprehension system depends upon obtaining information about how different types of knowledge are represented, accessed, and integrated during comprehension. The speed with which coprehension takes place neccessitates obtaining detailed information about the time course of comprehension. The proposed research explores the use of the cortical evoked potential as a technique for studying comprehension. Two sets of experiments are proposed. The first experiments examine the parsing process. Recent research using evoked potentials has identified a component of the waveform, N400, that is sensitive to whether or not a word is congruous with its context. Materials are developed in which alternative parsing models make different predictions about when and where in sentences local incongruities should develop. N400 is then used to test these predictions. The second series of experiments examine how context influences the recognition of a word by determining when the waveform of word and nonword stimuli diverge when words are presented in different types of linguistic context. These experiments will help us to better understand the organization of the language comprehension system. They will also provide a detailed evaluation of the value of the evoked potential as a methodology for studying comprehension processes. Finally, the use of well-defined linguistic stimuli in these experiments will help us to better understand how certain components of the evoked potential are related to cognitive processing.